Anti-vegfr antibody and uses thereof

ABSTRACT

The present invention relates to an antibody or antigen-binding fragment thereof that bind human vascular endothelial growth factor receptor 2 (VEGFR-2). The present invention also relates to a method for inhibiting VEGFR-2-mediated signaling in a subject in need, a method for treating diseases and/or disorders caused by or related to VEGFR-2 activity and/or signaling in a subject afflicted with the diseases and disorders, a method for treating tumor in a subject afflicted with the tumor, a method for inhibiting cell proliferation of endothelial cells in a subject in need, and a method for detecting human vascular endothelial growth factor receptor in a sample.

CROSS REFERENCE APPLICATION

This application claims the benefit of U.S. Provisional Patent Application 62/273,515 filed on 31 Dec. 2015 with the U.S. Patent and Trademark Office, the content of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an antibody or antigen-binding fragment thereof, which is specific to human vascular endothelial growth factor receptor (VEGFR), and uses thereof.

BACKGROUND OF THE INVENTION

The function of signal transduction pathway by vascular endothelial growth factor (VEGF) is promoting angiogenesis. Angiogenesis means the formation of new capillaries from original blood vessels. Abnormalities of angiogenesis regulation relate to pathogenic mechanisms of many diseases, and are also a feature of many types of cancer. The main roles participating in the signal transduction pathway are proteins belonging to a vascular endothelial growth factor family and receptors thereof. Activation of this signal transduction pathway activates complex networks downstream, and promotes the growth, migration and survival of vascular endothelial cells. This signaling transduction pathway is regarded as being closely connected to tumor angiogenesis, so the inhibition of signal transduction pathway is important for the regulation of tumor angiogenesis.

The vascular endothelial growth factor family comprises a group of homologous dimeric glycoproteins having highly conserved sequences. The members in the vascular endothelial growth factor family are activated by linking two 24 kDa single-stranded molecules through a disulfide bond. The known members in the vascular endothelial growth factor family include VEGF-A, VEGF-B, VEGF-C, VEGF-D, and placenta growth factor (PlGF), and wherein VEGF-A is first found and studied most thoroughly, which plays a critical role in angiogenesis.

When the vascular endothelial growth factor binds to vascular endothelial growth factor receptors (VEGF receptor, VEGFR), the vascular endothelial growth factor receptors form a dimer and phosphorylate each other. There are seven Ig-like domains located in the extracellular region of the vascular endothelial growth factor receptor. Generally, domains 1 to 3 are responsible for binding with the ligands, and domains 4 to 7 are responsible for dimerization, phosphorylation and downstream signal transduction.

The vascular endothelial growth factor receptor belongs to the tyrosine kinase (TK) family and is a key member in the signal transduction pathway. It transducts the extracellular signals of inducing cell growth, proliferation and anti-apoptosis into the cell. There are three types of the vascular endothelial growth factor receptor: VEGFR-1 (also known as flt-1), VEGFR-2 (also known as KDR/flk-1) and VEGFR-3 (also known as flt-4). VEGF-A binds to VEGFR-1 and VEGFR-2, and these two receptors are both expressed in the vascular endothelial cells, and the signals of the vascular endothelial cell are mainly transducted through VEGFR-2. Although the binding affinity between VEGFR-1 and the ligands is 10-folds stronger than that between VEGFR-2 and the ligands, the kinase activity of VEGFR-1 is weaker. In another aspect, VEGFR-3 is mainly expressed in lymphatic endothelial cells.

In addition to being by original peripheral vascular endothelial cell proliferation, it is also known that the tumor angiogenesis is formed by attracting vascular endothelial progenitor cells to move to the tumor or peripheral regions thereof under the regulation of VEGFR-2, and then the vascular endothelial progenitor cells are differentiated into the vascular endothelial cells. Because the angiogenesis relating to vascular endothelial growth factor receptor occurs only in wound repair and menstrual cycles of women in a normal physiological condition, the influence of blocking the signal transduction pathway by vascular endothelial growth factor receptor is limited to the normal physiological function. As a result, inhibiting signal transduction pathway by vascular endothelial growth factor receptor becomes an important regulatory point of inhibition of tumor angiogenesis and leading to tumor cell death consequently. It had been reported that vascular endothelial growth factors are over-expressed in a variety of solid tumors, such as colorectal cancer, breast cancer, prostate cancer, and lung cancer.

Thus, there is need for developing a novel approach to block signal transduction pathway by vascular endothelial growth factor receptor.

SUMMARY OF THE INVENTION

The present invention provides an antibody or antigen-binding fragment thereof that binds human vascular endothelial growth factor receptor 2 or a human vascular endothelial growth factor receptor 2 fragment. The antibody according to the invention are useful for inhibiting VEGFR-2-mediated signaling and for treating diseases and disorders caused by or related to VEGFR-2 activity and/or signaling. The antibody of the invention is also useful for inhibiting cell proliferation of endothelial cells.

The present invention provides a method for inhibiting VEGFR-2-mediated signaling in a subject in need, comprising administering to the subject a pharmaceutical composition comprising the antibody or antigen-binding fragment thereof as mentioned above.

The present invention provides a method for treating diseases and/or disorders caused by or related to VEGFR-2 activity and/or signaling in a subject afflicted with the diseases and/or disorders, comprising administering to the subject a pharmaceutical composition comprising the antibody or antigen-binding fragment thereof as mentioned above.

The present invention provides a method for treating tumor in a subject afflicted with the tumor, comprising administering to the subject a pharmaceutical composition comprising the antibody or antigen-binding fragment thereof as mentioned above.

The present invention provides a method for inhibiting cell proliferation of endothelial cells in a subject in need, comprising administering to the subject a pharmaceutical composition comprising the antibody or antigen-binding fragment thereof as mentioned above.

The present invention provides a method for detecting human vascular endothelial growth factor receptor in a sample comprising contacting the sample with the antibody or antigen-binding fragment thereof as mentioned above.

The present invention is described in detail in the following sections. Other characteristics, purposes and advantages of the present invention can be found in the detailed description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the ELISA result of binding affinity assay of the antibodies of the invention to mouse VEGFR-2, human VEGFR-1 or VEGFR-3.

FIG. 2 shows the ELISA result of binding domain mapping (domains 1 to 3 and domains 4 to 7) of the antibodies of the invention.

FIG. 3 shows the ELISA result of binding domain mapping of the antibodies of the invention.

FIG. 4 shows the ELISA result of epitope mapping of the antibodies of the invention.

FIG. 5 shows the HUVEC proliferation inhibition assay of the antibodies of the invention.

FIG. 6 shows the result of antibody internalization of the antibodies of the invention into HUVEC by flow cytometry.

FIG. 7 shows the result of antibody internalization observed with the DeltaVision Microscopy Imaging System.

FIG. 8 shows the result of size-exclusion chromatography analysis of the antibody-drug conjugate (ADC) according to the invention.

FIG. 9 shows the result of electrophoresis analysis of the antibody-drug conjugate according to the invention.

FIG. 10 shows the result of antibody internalization of the ADC according to the invention into HUVEC by flow cytometry.

FIG. 11 shows the HUVEC proliferation inhibition assay of the ADC of the invention.

FIG. 12 shows quantification assay of the chimeric antigen receptor T cell (CAR-T) according to the invention by flow cytometry.

FIG. 13 shows cytotoxicity assay of the chimeric antigen receptor T cell according to the invention.

FIG. 14 shows the efficiency of the labeling the antibodies according to the invention with radioisotope.

FIG. 15 shows the result of tumor detection in NanoSPECT/CT of HT-29 xenografted mice by the radio-labeled antibody according to the invention.

FIG. 16 shows the alignment of V_(L) segments of the humanized, mouse, and human antibodies. M: 322A6; Hd: Hu322B1HdH.

FIG. 17 shows the alignment of V_(H) segments of the humanized, mouse, and human antibodies. M: 322A6; Hu: human template IGHV1-46*01 F; HuB1: Hu322B1HdH.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an antibody or antigen-binding fragment thereof that binds to human vascular endothelial growth factor receptor 2 or a human vascular endothelial growth factor receptor 2 fragment.

Particularly, the antibody or antigen-binding fragment thereof according to the invention specifically binds to an epitope in human vascular endothelial growth factor receptor 2 or a fragment thereof; wherein the human vascular endothelial growth factor receptor 2 has the amino acid sequence of SEQ ID NO: 1, and the epitope comprises:

the leucine residue at position 606, the aspartic acid residue at position 607, the arginine residue at position 647, the lysine residue at position 648, and the threonine residue at position 649 of SEQ ID NO: 1; or the serine residue at position 711, the valine residue at position 714, and the arginine residues at positions 725 and 726 of SEQ ID NO: 1.

The antibody according to the invention can be full-length (for example, an IgG1 or IgG4 antibody) or may comprise only an antigen-binding portion (for example, a Fab, F(ab′)₂ or scFv fragment), and may be modified to affect functionality as needed.

The antibody or antigen-binding fragment thereof according to the invention specifically binds to human VEGFR-2. VEGFR-2, also known as KDR or flk-1, is a receptor of vascular endothelial growth factor, and is activated by forming a dimer and phosphorylating each other of the dimer when binds to the ligands thereof. VEGFR-2 comprises seven Ig-like domains located in the extracellular region, and wherein domains 1 to 3 are responsible for binding with the ligands, and domains 4 to 7 are responsible for dimerization, phosphorylation and downstream signal transduction. Preferably, the antibody or antigen-binding fragment thereof according to the invention binds to domains 6 to 7 of the extracellular region of VEGFR-2.

The present invention includes an anti-VEGFR-2 antibody and antigen-binding fragment thereof that binds monomeric or dimeric VEGFR-2 molecules with high affinity.

In one preferred embodiment of the invention, VEGFR-2 has the amino acid sequence of SEQ ID NO: 1; the domain 6 of the extracellular region of VEGFR-2 has the amino acid sequence of SEQ ID NO: 2; and the domain 7 of the extracellular region of VEGFR-2 has the amino acid sequence of SEQ ID NO: 3.

Various techniques known to persons of ordinary skill in the art can be used to determine whether an antibody “specifically binds to one or more amino acids” within a polypeptide or protein. Exemplary techniques include, e.g., routine cross-blocking assay such as that described Antibodies, Harlow and Lane (Cold Spring Harbor Press, Cold Spring Harb., N.Y.), alanine scanning mutational analysis, peptide blots analysis (Reineke, 2004, Methods Mol Biol 248:443-463), and peptide cleavage analysis. In addition, methods such as epitope excision, epitope extraction and chemical modification of antigens can be employed (Tomer, 2000, Protein Science 9:487-496). Another method that can be used to identify the amino acids within a polypeptide with which an antibody specifically binds is hydrogen/deuterium exchange detected by mass spectrometry. In general terms, the hydrogen/deuterium exchange method involves deuterium-labeling the protein of interest. followed by binding the antibody to the deuterium-labeled protein. Next, the protein/antibody complex is transferred to water to allow hydrogen-deuterium exchange to occur at all residues except for the residues protected by the antibody (which remain deuterium-labeled). After dissociation of the antibody, the target protein is subjected to protease cleavage and mass spectrometry analysis, thereby revealing the deuterium-labeled residues which correspond to the specific amino acids with which the antibody interacts. See, e.g., Ehring (1999) Analytical Biochemistry 267(2):252-259; Engen and Smith (2001) Anal. Chem. 73:256A-265A.

In one preferred embodiment of the invention, the epitope of VEGFR-2 comprises the leucine residue at position 606, the aspartic acid residue at position 607, the arginine residue at position 647, the lysine residue at position 648, and the threonine residue at position 649 of SEQ ID NO: 1.

In one another preferred embodiment of the invention, the epitope of VEGFR-2 comprises the serine residue at position 711, the valine residue at position 714, and the arginine residues at positions 725 and 726 of SEQ ID NO: 1.

The present invention further includes an anti-VEGFR antibody that specifically binds to the same epitope. Likewise, the present invention also includes an anti-VEGFR-2 antibody that competes for binding to VEGFR-2 with any of the specific exemplary antibodies described herein.

One can easily determine whether an antibody specifically binds to the same epitope as, or competes for binding with, a reference anti-VEGFR-2 antibody by using routine methods known in the art. For example, to determine if a test antibody binds to the same epitope as a reference anti-VEGFR-2 antibody of the invention, the reference antibody is allowed to bind to an VEGFR-2 protein (e.g., a soluble portion of the VEGFR-2 extracellular domain or cell surface-expressed VEGFR-2). Next, the ability of a test antibody to bind to the VEGFR-2 molecule is assessed. If the test antibody is able to bind to VEGFR-2 following saturation binding with the reference anti-VEGFR-2 antibody, it can be concluded that the test antibody binds to a different epitope than the reference anti-VEGFR-2 antibody. On the other hand, if the test antibody is not able to bind to the VEGFR-2 molecule following saturation binding with the reference anti-VEGFR-2 antibody, then the test antibody may bind to the same epitope as the epitope bound by the reference anti-VEGFR-2 antibody of the invention. Additional routine experimentation (e.g., peptide mutation and binding analyses) can then be carried out to confirm whether the observed lack of binding of the test antibody is in fact due to binding to the same epitope as the reference antibody or if steric blocking (or another phenomenon) is responsible for the lack of observed binding. Experiments of this sort can be performed using ELISA, RIA, Biacore, flow cytometry or any other quantitative or qualitative antibody-binding assay available in the art. In accordance with certain embodiments of the present invention, two antibodies bind to the same (or overlapping) epitope if, e.g., a 1-, 5-, 10-, 20- or 100-fold excess of one antibody inhibits binding of the other by at least 50% but preferably 75%, 90% or even 99% as measured in a competitive binding assay. Alternatively, two antibodies are deemed to bind to the same epitope if essentially all amino acid mutations in the antigen that reduce or eliminate binding of one antibody reduce or eliminate binding of the other. Two antibodies are deemed to have “overlapping epitopes” if only a subset of the amino acid mutations that reduce or eliminate binding of one antibody reduce or eliminate binding of the other.

To determine if an antibody competes for binding with a reference anti-VEGFR-2 antibody, the above-described binding methodology is performed in two orientations: In a first orientation, the reference antibody is allowed to bind to an VEGFR-2 protein (e.g., a soluble portion of the VEGFR-2 extracellular domain or cell surface-expressed VEGFR-2) under saturating conditions followed by assessment of binding of the test antibody to the VEGFR-2 molecule. In a second orientation, the test antibody is allowed to bind to a VEGFR-2 molecule under saturating conditions followed by assessment of binding of the reference antibody to the VEGFR-2 molecule. If, in both orientations, only the first (saturating) antibody is capable of binding to the VEGFR-2 molecule, then it is concluded that the test antibody and the reference antibody compete for binding to VEGFR-2. As will be appreciated by a person of ordinary skill in the art, an antibody that competes for binding with a reference antibody may not necessarily bind to the same epitope as the reference antibody, but may sterically block binding of the reference antibody by binding an overlapping or adjacent epitope.

The term “antibody”, as used herein, means any antigen-binding molecule or molecular complex comprising at least one complementarity determining region (CDR) that specifically binds to or interacts with a particular antigen (e.g., VEGFR-2). The term “antibody” includes immunoglobulin molecules comprising four polypeptide chains, two heavy (H) chains and two light (L) chains inter-connected by disulfide bonds, as well as multimers thereof (e.g., IgM). Each heavy chain comprises a heavy chain variable region (abbreviated herein as HCVR or V_(H)) and a heavy chain constant region. The heavy chain constant region comprises three domains, C_(H1), C_(H2) and C_(H3). Each light chain comprises a light chain variable region (abbreviated herein as LCVR or V_(L)) and a light chain constant region. The light chain constant region comprises one domain (C_(L1)). The V_(H) and V_(L) regions can be further subdivided into regions of hypervariability, termed complementarity determining regions (CDRs), interspersed with regions that are more conserved, termed framework regions (FR). Each V_(H) and V_(L) is composed of three CDRs and four FRs. arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. In different embodiments of the invention, the FRs of the anti-VEGFR antibody (or antigen-binding portion thereof) may be identical to the human germline sequences, or may be naturally or artificially modified. An amino acid consensus sequence may be defined based on a side-by-side analysis of two or more CDRs.

The term “antibody”, as used herein, also includes an antigen-binding fragment of a full antibody molecule. The terms “antigen-binding portion” of an antibody, “antigen-binding fragment” of an antibody, and the like, as used herein, include any naturally occurring, enzymatically obtainable, synthetic, or genetically engineered polypeptide or glycoprotein that specifically binds an antigen to form a complex. An antigen-binding fragment of an antibody may be derived, e.g., from full antibody molecules using any suitable standard techniques such as proteolytic digestion or recombinant genetic engineering techniques involving the manipulation and expression of DNA encoding antibody variable and optionally constant domains. Such DNA is known and/or is readily available from, e.g., commercial sources, DNA libraries (including, e.g., phage-antibody libraries), or can be synthesized. The DNA may be sequenced and manipulated chemically or by using molecular biology techniques, for example, to arrange one or more variable and/or constant domains into a suitable configuration, or to introduce codons, create cysteine residues, modify, add or delete amino acids, etc.

Non-limiting examples of an antigen-binding fragment includes: (i) Fab fragments; (ii) F(ab′)₂ fragments; (iii) Fd fragments; (iv) Fv fragments; (v) single-chain Fv (scFv) molecules; (vi) dAb fragments; and (vii) minimal recognition units consisting of the amino acid residues that mimic the hypervariable region of an antibody (e.g., an isolated complementarity determining region (CDR) such as a CDR3 peptide), or a constrained FR3-CDR3-FR4 peptide. Other engineered molecules, such as domain-specific antibodies, single domain antibodies, domain-deleted antibodies, chimeric antibodies, CDR-grafted antibodies, diabodies, triabodies, tetrabodies, minibodies, nanobodies (e.g. monovalent nanobodies, bivalent nanobodies, etc.), small modular immunopharmaceuticals (SMIPs), and shark variable IgNAR domains, are also encompassed within the expression “antigen-binding fragment,” as used herein.

An antigen-binding fragment of an antibody typically comprises at least one variable domain. The variable domain may be of any size or amino acid composition and will generally comprise at least one CDR which is adjacent to or in frame with one or more framework sequences. In antigen-binding fragments having a V_(H) domain associated with a V_(L) domain, the V_(H) and V_(L) domains may be situated relative to one another in any suitable arrangement. For example, the variable region may be dimeric and contain V_(H)-V_(H), V_(H)-V_(L) or V_(L)-V_(L) dimers. Alternatively, the antigen-binding fragment of an antibody may contain a monomeric V_(H) or V_(L) domain.

In certain embodiments, an antigen-binding fragment of an antibody may contain at least one variable domain covalently linked to at least one constant domain. Non-limiting, exemplary configurations of variable and constant domains that may be found within an antigen-binding fragment of an antibody of the present invention include: (i) V_(H)-C_(H1); (ii) V_(H)-C_(H2); (iii) V_(H)-C_(H3); (iv) V_(H)-CH_(H1)-C_(H2); (V) V_(H)-C_(H1)-C_(H2)-C_(H3), (vi) V_(H)-C_(H2)-C_(H3); (vii) V_(H)-C_(L); (viii) V_(L)-C_(H1); (ix) V_(L)-C_(H2); (x) V_(L)-C_(H3); (xi) V_(L)-C_(H1)-C_(H3); (xii) V_(L)-C_(H1)-C_(H2)-C_(H3); (xiii) V_(L)-C_(H2)-C_(H3); and (xiv) V_(L)-C_(L). In any configuration of variable and constant domains, including any of the exemplary configurations listed above, the variable and constant domains may be either directly linked to one another or may be linked by a full or partial hinge or linker region. A hinge region may consist of at least 2 (e.g., 5, 10, 15, 20, 40, 60 or more) amino acids which result in a flexible or semi-flexible linkage between adjacent variable and/or constant domains in a single polypeptide molecule. Moreover, an antigen-binding fragment of an antibody of the present invention may comprise a homo-dimer or hetero-dimer (or other multimer) of any of the variable and constant domain configurations listed above in non-covalent association with one another and/or with one or more monomeric V_(H) or V_(L) domain (e.g., by disulfide bond(s)).

As with a full antibody molecule, an antigen-binding fragment may be monospecific or multispecific (e.g., bispecific). A multispecific antigen-binding fragment of an antibody will typically comprise at least two different variable domains, wherein each variable domain is capable of specifically binding to a separate antigen or to a different epitope on the same antigen. Any multispecific antibody format, including the exemplary bispecific antibody formats disclosed herein, may be adapted for use in the context of an antigen-binding fragment of an antibody of the present invention using routine techniques available in the art.

Preferably, the antibody or antigen-binding fragment thereof according to the invention is a mammalian antibody.

The term “mammalian antibody”, as used herein, is intended to include antibodies having variable and constant regions derived from mammalian germline immunoglobulin sequences. The mammalian antibodies of the invention may include amino acid residues not encoded by mammalian germline immunoglobulin sequences (e.g., mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo), for example in the CDRs and in particular CDR3.

The term “recombinant mammalian antibody”, as used herein, is intended to include all mammalian antibodies that are prepared, expressed, created or isolated by recombinant means, such as antibodies expressed using a recombinant expression vector transfected into a host cell (described further below), antibodies isolated from a recombinant, combinatorial mammalian antibody library (described further below), antibodies isolated from an animal (e.g., a mouse) that is transgenic for mammalian immunoglobulin genes or antibodies prepared, expressed, created or isolated by any other means that involves splicing of mammalian immunoglobulin gene sequences to other DNA sequences. Such recombinant mammalian antibodies have variable and constant regions derived from mammalian germline immunoglobulin sequences. In certain embodiments, however, such recombinant mammalian antibodies are subjected to in vitro mutagenesis (or, when an animal transgenic for human Ig sequences is used, in vivo somatic mutagenesis) and thus the amino acid sequences of the V_(H) and V_(L) regions of the recombinant antibodies are sequences that, while derived from and related to human germline V_(H) and V_(L) sequences, may not naturally exist within the mammalian antibody germline repertoire in vivo.

Mammalian antibodies such as human antibodies can exist in two forms that are associated with hinge heterogeneity. In one form, an immunoglobulin molecule comprises a stable four chain construct of approximately 150-160 kDa in which the dimers are held together by an interchain heavy chain disulfide bond. In a second form, the dimers are not linked via inter-chain disulfide bonds and a molecule of about 75-80 kDa is formed composed of a covalently coupled light and heavy chain (half-antibody). These forms have been extremely difficult to separate, even after affinity purification.

The anti-VEGFR-2 antibody disclosed herein may comprise one or more amino acid substitutions, insertions and/or deletions in the framework and/or CDR regions of the heavy and light chain variable domains as compared to the corresponding germline sequences from which the antibodies were derived. Such mutations can be readily ascertained by comparing the amino acid sequences disclosed herein to germline sequences available from, for example, public antibody sequence databases. The present invention includes an antibody, and an antigen-binding fragment thereof, which are derived from any of the amino acid sequences disclosed herein, wherein one or more amino acids within one or more framework and/or CDR regions are mutated to the corresponding residue(s) of the germline sequence from which the antibody was derived, or to the corresponding residue(s) of another mammalian germline sequence, or to a conservative amino acid substitution of the corresponding germline residue(s) (such sequence changes are referred to herein collectively as “germline mutations”). A person of ordinary skill in the art, starting with the heavy and light chain variable region sequences disclosed herein, can easily produce numerous antibodies and antigen-binding fragments which comprise one or more individual germline mutations or combinations thereof. In certain embodiments, all of the framework and/or CDR residues within the V_(H) and/or V_(L) domains are mutated back to the residues found in the original germline sequence from which the antibody was derived. In other embodiments, only certain residues are mutated back to the original germline sequence, e.g., only the mutated residues found within the first 8 amino acids of FR1 or within the last 8 amino acids of FR4, or only the mutated residues found within CDR1, CDR2 or CDR3. In other embodiments, one or more of the framework and/or CDR residue(s) are mutated to the corresponding residue(s) of a different germline sequence (i.e., a germline sequence that is different from the germline sequence from which the antibody was originally derived). Furthermore, the antibodies of the present invention may contain any combination of two or more germline mutations within the framework and/or CDR regions, e.g., wherein certain individual residues are mutated to the corresponding residue of a particular germline sequence while certain other residues that differ from the original germline sequence are maintained or are mutated to the corresponding residue of a different germline sequence. Once obtained, antibodies and antigen-binding fragments that contain one or more germline mutations can be easily tested for one or more desired property such as, improved binding specificity, increased binding affinity, improved or enhanced antagonistic or agonistic biological properties (as the case may be), reduced immunogenicity, etc. Antibodies and antigen-binding fragments obtained in this general manner are encompassed within the present invention.

The present invention also includes an anti-VEGFR-2 antibody comprising variants of any of the V_(H), V_(L), and/or CDR amino acid sequences disclosed herein having one or more conservative substitutions. For example, the present invention includes an anti-VEGFR-2 antibody having V_(H), V_(L), and/or CDR amino acid sequences with, e.g., 10 or fewer, 8 or fewer, 6 or fewer, 4 or fewer, etc. conservative amino acid substitutions relative to any of the V_(H), V_(L), and/or CDR amino acid sequences disclosed herein.

The term “substantial identity” or “substantially identical,” when referring to a nucleic acid or fragment thereof, indicates that, when optimally aligned with appropriate nucleotide insertions or deletions with another nucleic acid (or its complementary strand), there is nucleotide sequence identity in at least about 95%, and more preferably at least about 96%, 97%, 98% or 99% of the nucleotide bases, as measured by any well-known algorithm of sequence identity, such as FASTA, BLAST or Gap, as discussed below. A nucleic acid molecule having substantial identity to a reference nucleic acid molecule may, in certain instances, encode a polypeptide having the same or substantially similar amino acid sequence as the polypeptide encoded by the reference nucleic acid molecule.

As applied to polypeptides, the term “substantial similarity” or “substantially similar” means that two peptide sequences, when optimally aligned, such as by the programs GAP or BESTFIT using default gap weights, share at least 95% sequence identity, even more preferably at least 98% or 99% sequence identity. Preferably, residue positions which are not identical differ by conservative amino acid substitutions. A “conservative amino acid substitution” is one in which an amino acid residue is substituted by another amino acid residue having a side chain (R group) with similar chemical properties (e.g., charge or hydrophobicity). In general, a conservative amino acid substitution will not substantially change the functional properties of a protein. In cases where two or more amino acid sequences differ from each other by conservative substitutions, the percent sequence identity or degree of similarity may be adjusted upwards to correct for the conservative nature of the substitution. Means for making this adjustment are well-known to those of skill in the art. Examples of groups of amino acids that have side chains with similar chemical properties include (1) aliphatic side chains: glycine, alanine, valine, leucine and isoleucine; (2) aliphatic-hydroxyl side chains: serine and threonine; (3) amide-containing side chains: asparagine and glutamine; (4) aromatic side chains: phenylalanine, tyrosine, and tryptophan; (5) basic side chains: lysine, arginine, and histidine; (6) acidic side chains: aspartate and glutamate, and (7) sulfur-containing side chains are cysteine and methionine. Preferred conservative amino acids substitution groups are: valine-leucine-isoleucine, phenylalanine-tyrosine, lysine-arginine, alanine-valine, glutamate-aspartate, and asparagine-glutamine. Alternatively, a conservative replacement is any change having a positive value in the PAM250 log-likelihood matrix disclosed in Gonnet et al. (1992) Science 256: 1443-1445, herein incorporated by reference. A “moderately conservative” replacement is any change having a nonnegative value in the PAM250 log-likelihood matrix.

Sequence similarity for polypeptides, which is also referred to as sequence identity, is typically measured using sequence analysis software. Protein analysis software matches similar sequences using measures of similarity assigned to various substitutions, deletions and other modifications, including conservative amino acid substitutions. For instance, GCG software contains programs such as Gap and Bestfit which can be used with default parameters to determine sequence homology or sequence identity between closely related polypeptides, such as homologous polypeptides from different species of organisms or between a wild type protein and a mutant thereof. Polypeptide sequences also can be compared using FASTA using default or recommended parameters, a program in GCG Version 6.1. FASTA (e.g., FASTA2 and FASTA3) provides alignments and percent sequence identity of the regions of the best overlap between the query and search sequences (Pearson (2000) supra). Another preferred algorithm when comparing a sequence of the invention to a database containing a large number of sequences from different organisms is the computer program BLAST, especially BLASTP or TBLASTN, using default parameters. See, e.g., Altschul et al. (1990) J. Mol. Biol. 215:403-410 and Altschul et al. (1997) Nucleic Acids Res. 25:3389-402, each herein incorporated by reference.

In one preferred embodiment of the invention, the antibody or antigen-binding fragment thereof comprises complementarity determining regions of a heavy chain variable region and complementarity determining regions of a light chain variable region, wherein the complementarity determining regions of the heavy chain variable region comprises CDRH1, CDRH2 and CDRH3 regions, and the complementarity determining regions of the light chain variable region comprises CDRL1, CDRL2 and CDRL3 regions, and

the CDRH1 region comprises the amino acid sequence of SEQ ID NO: 4, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; the CDRH2 region comprises the amino acid sequence of SEQ ID NO: 5, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; the CDRH3 region comprises the amino acid sequence of SEQ ID NO: 6, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; the CDRL1 region comprises the amino acid sequence of SEQ ID NO: 7, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; the CDRL2 region comprises the amino acid sequence of SEQ ID NO: 8, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; and the CDRL3 region comprises the amino acid sequence of SEQ ID NO: 9, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99%, sequence identity.

In one another preferred embodiment of the invention, the antibody or antigen-binding fragment thereof comprises complementarity determining regions of a heavy chain variable region and complementarity determining regions of a light chain variable region, wherein the complementarity determining regions of the heavy chain variable region comprises CDRH1, CDRH2 and CDRH3 regions, and the complementarity determining regions of the light chain variable region comprises CDRL1, CDRL2 and CDRL3 regions, and

the CDRH1 region comprises the amino acid sequence of SEQ ID NO: 10, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; the CDRH2 region comprises the amino acid sequence of SEQ ID NO: 11, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; the CDRH3 region comprises the amino acid sequence of SEQ ID NO: 12, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; the CDRL1 region comprises the amino acid sequence of SEQ ID NO: 13, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 990% sequence identity; the CDRL2 region comprises the amino acid sequence of SEQ ID NO: 14, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; and the CDRL3 region comprises the amino acid sequence of SEQ ID NO: 15, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity.

In one preferred embodiment of the invention, an antibody 322A6 or antigen-binding fragment thereof comprises a heavy chain variable region comprising the amino acid sequences of SEQ ID NO: 17 or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity. Preferably, the heavy chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 16. The 322A6 or antigen-binding fragment thereof comprises a light chain variable region comprising the amino acid sequence of SEQ ID NO: 19 or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity or a substantially similar sequence thereof. Preferably, the light chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 18.

In one preferred embodiment of the invention, an antibody 12A6 or antigen-binding fragment thereof comprises a heavy chain variable region comprising the amino acid sequences of SEQ ID NO: 21 or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity. Preferably, the heavy chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 20. The 12A6 or antigen-binding fragment thereof comprises a light chain variable region comprising the amino acid sequence of SEQ ID NO: 23 or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity or a substantially similar sequence thereof. Preferably, the light chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 22.

In another aspect, the antibody according to the invention is preferably a humanized antibody. A “humanized antibody” is a recombinant protein in which the CDRs from an antibody from one species, e.g., a rodent antibody, are transferred from the heavy and light variable chains of the rodent antibody into human heavy and light variable domains, including human framework region (FR) sequences. The constant domains of the antibody molecule are derived from those of a human antibody.

In order to improve the binding affinity of the humanized antibody according to the invention, some amino acid residues in the human framework region are replaced by the corresponding amino acid residues in the species of CDRs; e.g. a rodent. Preferably, a humanized antibody Hu322B1HdH or antigen-binding fragment thereof comprises a heavy chain variable region comprising the amino acid sequences of SEQ ID NO: 25 or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity. Preferably, the heavy chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 24. The Hu322B1HdH or antigen-binding fragment thereof comprises a light chain variable region comprising the amino acid sequence of SEQ ID NO: 27 or a substantially similar sequence thereof having at least 90° %, at least 95%, at least 98% or at least 99% sequence identity or a substantially similar sequence thereof. Preferably, the light chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 26.

Preferably, the antibody according to the invention is a monoclonal antibody.

The antibodies of the present invention may be monospecific, bi-specific, or multispecific. Multispecific antibodies may be specific for different epitopes of one target polypeptide or may contain antigen-binding domains specific for more than one target polypeptide. The anti-VEGFR-2 antibodies of the present invention can be linked to or co-expressed with another functional molecule, e.g., another peptide or protein. For example, an antibody or fragment thereof can be functionally linked (e.g., by chemical coupling, genetic fusion, noncovalent association or otherwise) to one or more other molecular entities, such as another antibody or antibody fragment to produce a bi-specific or a multispecific antibody with a second binding specificity. For example, the present invention includes bi-specific antibodies wherein one arm of an immunoglobulin is specific for human VEGFR-2 or a fragment thereof, and the other arm of the immunoglobulin is specific for a second therapeutic target or is conjugated to a therapeutic moiety.

In one preferred embodiment of the invention, the antibody or antigen-binding fragment thereof is conjugated with a therapeutic agent.

As used herein, a “therapeutic agent” represents a cytostatic or cytotoxic agent or an isotope-chelating agent with corresponding radioisotopes. Examples of the cytostatic or cytotoxic agent include, without limitation, antimetabolites (e.g., fluorouracil (5-FU), floxuridine (5-FUdR), methotrexate, leucovorin, hydroxyurea, thioguanine (6-TG), mercaptopurine (6-MP), cytarabine, pentostatin, fludarabine phosphate, cladribine (2-CDA), asparaginase, gemcitabine, capecitibine, azathioprine, cytosine methotrexate, trimethoprim, pyrimethamine, or pemetrexed); alkylating agents (e.g., cmelphalan, chlorambucil, busulfan, thiotepa, ifosfamide, carmustine, lomustine, semustine, streptozocin, dacarbazine, mitomycin C, cyclophosphamide, mechlorethamine, uramustine, dibromomannitol, tetranitrate, procarbazine, altretamine, mitozolomide, or temozolomide); alkylating-like agents (e.g., cisplatin, carboplatin, nedaplatin, oxaliplatin, satraplatin, or triplatin); DNA minor groove alkylating agents (e.g., duocarmycins such as CC-1065, and any analogs or derivatives thereof; pyrrolobenzodiazapenes, or any analogs or derivatives thereof); anthracyclines (e.g., daunorubicin, doxorubicin, epirubicin, idarubicin, or valrubicin); antibiotics (e.g., dactinomycin, bleomycin, mithramycin, anthramycin, streptozotocin, gramicidin D, mitomycins (e.g., mitomycin C); calicheamicins; antimitotic agents (including, e.g., maytansinoids (such as DM1, DM3, and DM4), auristatins (including, e.g., monomethyl auristatin E (MMAE) and monomethyl auristatin F (MMAF)), dolastatins, cryptophycins, vinca alkaloids (e.g., vincristine, vinblastine, vindesine, vinorelbine), taxanes (e.g., paclitaxel, docetaxel, or a novel taxane), tubulysins, and colchicines); topoisomerase inhibitors (e.g., irinotecan, topotecan, camptothecin, etoposide, teniposide, amsacrine, or mitoxantrone); HDAC inhibitor (e.g., vorinostat, romidepsin, chidamide, panobinostat, or belinostat); proteasome inhibitors (e.g., peptidyl boronic acids); as well as radioisotopes such as At²¹¹, I¹³¹, I¹²⁵, Y⁹⁰, Re¹⁷⁵, Re¹⁸⁸, Sm¹⁵³, Bi²¹² or ²¹³, P³² and radioactive isotopes of Lu including Lu¹⁷⁷. Examples of the isotope-chelating agents include, without limitation, ethylenediaminetetraacetic acid (EDTA), diethylenetriamine-N,N,N′,N″,N″-pentaacetate (DTPA), 1,4,7,10-tetraazacyclododecane-N,N′,N″,N′″-tetraacetate (DOTA), 1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane (THP), triethylenetetraamine-N,N,N′,N″,N′″,N′″-hexaacetate (TTHA), 1,4,7,10-tetraazacyclododecane-N,N′,N″,N′″-tetrakis(methylenephosphonate) (DOTP), and mercaptoacetyltriglycine (MAG3).

In one preferred embodiment of the invention, the antibody or antigen-binding fragment thereof can be produced using any number of expression systems, including prokaryotic and eukaryotic expression systems. In some embodiments, the expression system is a mammalian cell expression, such as a hybridoma, or a CHO cell expression system. Many such systems are widely available from commercial suppliers. In embodiments in which an antibody comprises both a V_(H) and V_(L) region, the V_(H) and V_(L) regions may be expressed using a single vector, e.g., in a di-cistronic expression unit, or under the control of different promoters. In other embodiments, the V_(H) and V_(L) region may be expressed using separate vectors. A V_(H) or V_(L) region as described herein may optionally comprise a methionine at the N-terminus.

The genes encoding the heavy and light chains of an antibody of interest can be cloned from a cell, e.g., the genes encoding a monoclonal antibody can be cloned from a hybridoma and used to produce a recombinant monoclonal antibody. Gene libraries encoding heavy and light chains of monoclonal antibodies can also be made from hybridoma or plasma cells. Random combinations of the heavy and light chain gene products generate a large pool of antibodies with different antigenic specificity (see, e.g., Kuby, Immunology (3.sup.rd ed. 1997)).

Techniques for the production of single chain antibodies or recombinant antibodies (U.S. Pat. No. 4,946,778, U.S. Pat. No. 4,816,567) can be adapted to produce antibodies to polypeptides of this invention. Also, transgenic mice, or other organisms such as other mammals, can be used to express humanized or human antibodies (see, e.g., U.S. Pat. Nos. 5,545,807; 5,545,806; 5,569,825; 5,625,126; 5,633,425; 5,661,016, Marks et al., Bio/Technology 10:779-783 (1992); Lonberg et al., Nature 368:856-859 (1994); Morrison, Nature 368:812-13 (1994); Fishwild et al., Nature Biotechnology 14:845-51 (1996); Neuberger, Nature Biotechnology 14:826 (1996); and Lonberg & Huszar, Intern. Rev. Immunol. 13:65-93 (1995)).

In one preferred embodiment of the invention, the antibody or antigen-binding fragment thereof is expressed on a surface of a cell. More preferably, the cell is a T-cell.

The invention provides pharmaceutical compositions comprising the anti-VEGFR-2 antibody or antigen-binding fragment thereof of the present invention. The pharmaceutical compositions of the invention are formulated with suitable carriers, excipients, and other agents that provide improved transfer, delivery, tolerance, and the like. A multitude of appropriate formulations can be found in the formulary known to all pharmaceutical chemists: Remington's Pharmaceutical Sciences, Mack Publishing Company, Easton, Pa. These formulations include, for example, powders, pastes, ointments, jellies, waxes, oils, lipids, lipid (cationic or anionic) containing vesicles (such as LIPOFECTIN™, Life Technologies, Carlsbad, Calif.), DNA conjugates, anhydrous absorption pastes, oil-in-water and water-in-oil emulsions, emulsions carbowax (polyethylene glycols of various molecular weights), semi-solid gels, and semi-solid mixtures containing carbowax. See also Powell et al. “Compendium of excipients for parenteral formulations” PDA (1998) J Pharm Sci Technol 52:238-311.

The dose of antibody administered to a patient may vary depending upon the age and the size of the patient, target disease, conditions, route of administration, and the like. The preferred dose is typically calculated according to body weight or body surface area. When an antibody of the present invention is used for treating a condition or disease associated with VEGFR-2 activity in an adult patient, it may be advantageous to intravenously administer the antibody of the present invention normally at a single dose of about 0.01 to about 20 mg/kg body weight, more preferably about 0.02 to about 7, about 0.03 to about 5, or about 0.05 to about 3 mg/kg body weight. Depending on the severity of the condition, the frequency and the duration of the treatment can be adjusted. Effective dosages and schedules for administering anti-VEGFR-2 antibody may be determined empirically; for example, patient progress can be monitored by periodic assessment, and the dose adjusted accordingly. Moreover, interspecies scaling of dosages can be performed using well-known methods in the art (e.g., Mordenti et al., 1991, Pharmaceut. Res. 8:1351).

Various delivery systems are known and can be used to administer the pharmaceutical composition of the invention, e.g., encapsulation in liposomes, microparticles, microcapsules, recombinant cells capable of expressing the mutant viruses, receptor mediated endocytosis (see, e.g., Wu et al., 1987, J. Biol. Chem. 262:4429-4432). Methods of introduction include, but are not limited to, intradermal, intramuscular, intraperitoneal, intravenous, subcutaneous, intranasal, epidural, and oral routes. The composition may be administered by any convenient route, for example by infusion or bolus injection, by absorption through epithelial or mucocutaneous linings (e.g., oral mucosa, rectal and intestinal mucosa, etc.) and may be administered together with other biologically active agents. Administration can be systemic or local.

A pharmaceutical composition of the present invention can be delivered subcutaneously or intravenously with a standard needle and syringe. In addition, with respect to subcutaneous delivery, a pen delivery device readily has applications in delivering a pharmaceutical composition of the present invention. Such a pen delivery device can be reusable or disposable. A reusable pen delivery device generally utilizes a replaceable cartridge that contains a pharmaceutical composition. Once all of the pharmaceutical composition within the cartridge has been administered and the cartridge is empty, the empty cartridge can readily be discarded and replaced with a new cartridge that contains the pharmaceutical composition. The pen delivery device can then be reused. In a disposable pen delivery device, there is no replaceable cartridge. Rather, the disposable pen delivery device comes prefilled with the pharmaceutical composition held in a reservoir within the device. Once the reservoir is emptied of the pharmaceutical composition, the entire device is discarded.

In certain situations, the pharmaceutical composition can be delivered in a controlled release system. In one embodiment, a pump may be used (see Langer, supra; Sefton, 1987, CRC Crit. Ref. Biomed. Eng. 14:201). In another embodiment, polymeric materials can be used; see, Medical Applications of Controlled Release, Langer and Wise (eds.), 1974, CRC Pres., Boca Raton, Fla. In yet another embodiment, a controlled release system can be placed in proximity of the composition's target, thus requiring only a fraction of the systemic dose (see, e.g., Goodson, 1984, in Medical Applications of Controlled Release, supra, vol. 2, pp. 115-138). Other controlled release systems are discussed in the review by Langer, 1990, Science 249:1527-1533.

The injectable preparations may include dosage forms for intravenous, subcutaneous, intracutaneous and intramuscular injections, drip infusions, etc. These injectable preparations may be prepared by methods publicly known. For example, the injectable preparations may be prepared, e.g., by dissolving, suspending or emulsifying the antibody or its salt described above in a sterile aqueous medium or an oily medium conventionally used for injections. As the aqueous medium for injections, there are, for example, physiological saline, an isotonic solution containing glucose and other auxiliary agents, etc., which may be used in combination with an appropriate solubilizing agent such as an alcohol (e.g., ethanol), a polyalcohol (e.g., propylene glycol, polyethylene glycol), a nonionic surfactant [e.g., polysorbate 80, HCO-50 (polyoxyethylene (50 mol) adduct of hydrogenated castor oil)], etc. As the oily medium, there are employed, e.g., sesame oil, soybean oil, etc., which may be used in combination with a solubilizing agent such as benzyl benzoate, benzyl alcohol, etc. The injection thus prepared is preferably filled in an appropriate ampoule.

Advantageously, the pharmaceutical compositions for oral or parenteral use described above are prepared into dosage forms in a unit dose suited to fit a dose of the active ingredients. Such dosage forms in a unit dose include, for example, tablets, pills, capsules, injections (ampoules), suppositories, etc. The amount of the aforesaid antibody contained is generally about 5 to about 500 mg per dosage form in a unit dose; especially in the form of injection, it is preferred that the aforesaid antibody is contained in about 5 to about 100 mg and in about 10 to about 250 mg for the other dosage forms.

The antibody according to the invention is useful for inhibiting VEGFR-mediated signaling and for treating diseases and disorders caused by or related to VEGFR-2 activity and/or signaling. The antibody of the invention is also useful for inhibiting cell proliferation of endothelial cells.

The present invention provides a method for inhibiting VEGFR-2-mediated signaling in a subject in need, comprising administering to the subject a pharmaceutical composition comprising the antibody or antigen-binding fragment thereof as mentioned above.

The present invention provides a method for treating diseases and/or disorders caused by or related to VEGFR-2 activity and/or signaling in a subject afflicted with the diseases and/or disorders, comprising administering to the subject a pharmaceutical composition comprising the antibody or antigen-binding fragment thereof as mentioned above.

The present invention provides a method for treating tumor in a subject afflicted with the tumor, comprising administering to the subject a pharmaceutical composition comprising the antibody or antigen-binding fragment thereof as mentioned above.

The present invention provides a method for inhibiting cell proliferation of endothelial cells in a subject in need, comprising administering to the subject a pharmaceutical composition comprising the antibody or antigen-binding fragment thereof as mentioned above.

The terms “treating” and “treatment” as used herein refer to the administration of an agent or formulation to a clinically symptomatic individual afflicted with an adverse condition, disorder, or disease, so as to effect a reduction in severity and/or frequency of symptoms, eliminate the symptoms and/or their underlying cause, and/or facilitate improvement or remediation of damage. The terms “preventing” and “prevention” refer to the administration of an agent or composition to a clinically asymptomatic individual who is susceptible to a particular adverse condition, disorder, or disease, and thus relates to the prevention of the occurrence of symptoms and/or their underlying cause. As is understood by one skilled in the art, prevention or preventing need not achieve absolute (complete) block or avoidance of the conditions. Rather, prevention may achieve substantial (e.g., over about 50%) reduction or avoidance of the diseases or conditions to be prevented. Unless otherwise indicated herein, either explicitly or by implication, if the term “treatment” (or “treating”) is used without reference to possible prevention, it is intended that prevention be encompassed as well.

“Cancer,” “tumor,” “transformed” and like terms include precancerous, neoplastic, transformed, and cancerous cells, and can refer to a solid tumor, or a non-solid cancer (see, e.g., Edge et al. AJCC Cancer Staging Manual (7th ed. 2009), Cibas and Ducatman Cytology: Diagnostic principles and clinical correlates (3rd ed. 2009)). Cancer includes both benign and malignant neoplasms (abnormal growth). “Transformation” refers to spontaneous or induced phenotypic changes, e.g., immortalization of cells, morphological changes, aberrant cell growth, reduced contact inhibition and anchorage, and/or malignancy (see, Freshney, Culture of Animal Cells a Manual of Basic Technique (3rd ed. 1994)). Although transformation can arise from infection with a transforming virus and incorporation of new genomic DNA, or uptake of exogenous DNA, it can also arise spontaneously or following exposure to a carcinogen.

The antibody of the invention is useful, inter alia, for the treatment, prevention and/or amelioration of any disease or disorder associated with or mediated by VEGFR-2 expression or activity, or treatable by blocking the interaction between VEGFR-2 and a VEGFR-2 ligand or otherwise inhibiting VEGFR-2 activity and/or signaling, and/or promoting receptor internalization and/or decreasing cell surface receptor number. For example, the antibody and antigen-binding fragment of the present invention are useful for the treatment of tumors that express high levels of VEGFR-2. The antibody and antigen-binding fragment of the present invention may be used to treat, e.g., primary and/or metastatic tumors arising in the brain and meninges, oropharynx, lung and bronchial tree, gastrointestinal tract, male and female reproductive tract, muscle, bone, skin and appendages, connective tissue, spleen, immune system, blood forming cells and bone marrow, liver and urinary tract, and special sensory organs such as the eye. In certain embodiments, the antibody and antigen-binding fragment of the invention are used to treat one or more of the following cancers: renal cell carcinoma, pancreatic carcinoma, breast cancer, head and neck cancer, prostate cancer, malignant gliomas, osteosarcoma, colorectal cancer, gastric cancer (e.g., gastric cancer with MET amplification), malignant mesothelioma, multiple myeloma, ovarian cancer, small cell lung cancer, non-small cell lung cancer (e.g., VEGFR-2-dependent non-small cell lung cancer), synovial sarcoma, thyroid cancer, or melanoma.

The present invention provides a method for detecting human vascular endothelial growth factor receptor in a sample comprising contacting the sample with the antibody or antigen-binding fragment thereof as mentioned above.

The anti-VEGFR-2 antibody of the present invention may also be used to detect and/or measure VEGFR-2, or VEGFR-2-expressing cells in a sample, e.g., for diagnostic purposes. For example, an anti-VEGFR-2 antibody, or fragment thereof, may be used to diagnose a condition or disease characterized by aberrant expression (e.g., over-expression, under-expression, lack of expression, etc.) of VEGFR-2. Exemplary diagnostic assays for VEGFR-2 may comprise, e.g., contacting a sample, obtained from a patient, with an anti-VEGFR-2 antibody of the invention, wherein the anti-VEGFR-2 antibody is labeled with a detectable label or reporter molecule. Alternatively, an unlabeled anti-VEGFR-2 antibody can be used in diagnostic applications in combination with a secondary antibody which is itself detectably labeled. The detectable label or reporter molecule can be a radioisotope, such as ³H, ¹⁴C, ³²P, ³⁵S, or ¹²⁵I; a fluorescent or chemiluminescent moiety such as fluorescein isothiocyanate, or rhodamine; or an enzyme such as alkaline phosphatase, beta-galactosidase, horseradish peroxidase, or luciferase. Specific exemplary assays that can be used to detect or measure VEGFR-2 in a sample include enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA), and fluorescence-activated cell sorting (FACS).

Samples that can be used in VEGFR-2 diagnostic assays according to the present invention include any tissue or fluid sample obtainable from a patient which contains detectable quantities of VEGFR-2 protein, or fragments thereof, under normal or pathological conditions. Generally, levels of VEGFR-2 in a particular sample obtained from a healthy patient (e.g., a patient not afflicted with a disease or condition associated with abnormal VEGFR-2 levels or activity) will be measured to initially establish a baseline, or standard, level of VEGFR-2. This baseline level of VEGFR-2 can then be compared against the levels of VEGFR-2 measured in samples obtained from individuals suspected of having a VEGFR-2 related disease or condition.

The following examples are provided to aid those skilled in the art in practicing the present invention.

EXAMPLES Construction of scFv/Fab Antibody Library

VEGFR2-Fc-His, a fusion protein containing the sequence of SEQ ID NO: 1 was used as an antigen to immune a mouse 6 times every two weeks. After immunization, the mouse was sacrificed and the spleen was obtained. Total RNAs of the spleen were extracted and reverse transcripted in an RT-PCR procedure with the primers to construct antibody fragments containing V_(H), V_(L), V_(H)-CH1, V_(L)-CL. The antibody fragments were assembled into scFv fragments in polymerase chain reactions and a scFv library was constructed. To begin with, the Fab library was constructed with a V_(L)-CL library from V_(L)-CL fragments into a plasmid. Next, V_(H)-CH1 fragments were constructed into the plasmid containing the V_(L)-CL fragments to general the final Fab library.

Preparation of scFv/Fab Phage for Bio-Panning

The obtained library was inoculated into a 2×YT medium containing 100 μg/ml ampicillin and 2% glucose (2YTAG) and incubated with shaking at 37° C. until the OD at 600 nm reaching 0.5. The culture was infected with a helper phage and then cultured without shaking in a 37° C. water bath for 30 min. The cells were collected and suspended in a 2×YT medium containing 100 pg/ml ampicillin and 25 pg/ml kanamycin (2YTAK) and further incubated with shaking at 30° C. overnight. The supernatant of the culture was collected and mixed with 1/5 volume of PEG/NaCl (20% Polyethylene glycol 8000, 2.5 M NaCl) and stayed for 1 hr or more at 4° C. After centrifuging, the pellet was collected and suspended in 40 mL of PBS and spun again to collect the supernatant.

Selection Using ELISA Method

An ELISA plate (Nunc) was coated with 1 μg/100 μL of antigen per well and stayed in sodium bicarbonate buffer, pH 9.6 at 4° C. overnight. The wells were washed 3 times with PBS and blocked with 300 μL of PBS-5% skim milk (MPBS) per well at 37° C. for 1.5 hr. After washed 3 times with PBS, 100 μL of phages in 5% MPBS with fusion protein contains his-tag were added and incubated at 37° C. for 90 min. After washed 10 times with PBS-0.05% Tween 20 (PBST) and 10 times PBS, the phages were eluted by adding 100 μL of 100 mM triethylamine (TEA) and reacted at 37° C. for 30 min. One-hundred μL of eluted phages were neutralized with 50 μL of 1 M Tris, pH 7.4. Ten ml of TG1 at an exponentially growing stage were added to 150 μL of the eluted phages. The cultures were incubated at 37° C. for 30 min without shaking for infection. The infected TG1 bacteria were spun and collected and then suspended in 2×YT and plated on a 2×YT-AG plate. The bacteria were incubated at 30° C. overnight.

Selection Using Dynabeads Method

In a pre-clean phage step, Dynabeads were pre-washed with 1 ml of PBS three times, and suspended in PBS. Then, 0.3 mL of the phages were mixed with 0.5 ml of 5% MPBS, fusion protein contains his-tag and incubated on a rotator for 30 min, and then Dynabeads were removed.

The Dynabeads were reacted with biotin-labeled VEGFR2-His for 90 min. The Dynabeads were washed with 1 ml of PBS three times and suspended in 5% MPBS and incubated for 90 min and then washed with 1 ml of PBS three times. The pre-clean phage was added to the VEGFR2-His with Dynabeads and incubated on a rotator for another 30 min. The Dynabeads were then washed with 1 ml of 0.05% PBST, 0.2% MPBS, and PBS. The bound phages were eluted with 1 ml of 100 mM TEA. For quick neutralization, 0.5 ml of 1M Tris, pH 7.4 was added to the eluted phages. Then, 6 ml of an exponentially growing culture of TG1 was taken and the TEA eluted phages were added. The cultures were incubated for 30 min at 37° C. (water bath) without shaking. The infected TG1 bacterial were pooled and spun for collecting the pellet. The pelleted bacteria were suspended in 1 ml of 2×YT and plated on a large 2×YT-AG plate. The bacteria were incubated at 30° C. overnight.

Preparation of Next Round Phage

Five to six ml of 2×YT, 15% glycerol was added to the bacterial plate and the colonies were loosed with a glass spreader. Then, 10 μl of the scraped bacteria were added to 10 ml of 2×YT-AG and the bacteria grew with shaking at 37° C. until the OD at 600 nm reaching 0.5. Ten ml of the culture was infected with M13KO7 helper phage by adding the helper phage in the ratio of 1:20 and the infected culture was incubated without shaking in a 37° C. water bath for 30 min. The cultures were spun to collect the pellet, and the pellet was suspension with 50 mL of 2×YT-AK and then cultured at 30° C. overnight. Further, 40 ml of the overnight culture was spun at 10,000 rpm for 20 min to collect the supernatant, and 1/5 volume (8 ml) PEG/NaCl was added to the supernatant. The well was mixed and left for 1 hr or more at 4° C. The mixture was spun at 10,000 rpm for 20 min and the pellet was collected and suspended in 2 ml PBS. The suspension was spun at 12000 rpm for 10 min to remove most of the remaining bacterial debris.

Screening of VEGFR2-Positive Phage by ELISA

The individual colonies from the plate were inoculated into 200 μl of 2×YT-AG 96-well plates and grew with shaking overnight at 37° C. and then 50 ul transferred to a second 96-well plate containing 200 μl of 2×YT-AG per well for shaking at 37° C. for 2 hr. Then, 50 μl of 2×YT-AG with 10⁹ pfu M13KO7 helper phage was added to each well of the second plate. The mixture was stood for 30 min at 37° C. and then shaken for 1 hr at 37° C. After spun at 4000 rpm for 30 min, and the supernatant was aspirated off, and the pellet was suspended in 300 μl of 2×YT-AK for growing with shaking overnight at 30° C. The culture was spun at 4000 rpm for 30 min and 100 pi of the culture supernatant was taken for phage ELISA.

The ELISA plates were coated with 1 μg/mL per well of protein antigen, and then rinsed 3 times with PBS, and blocked with 300 μl of 2% MPBS per well for 2 hr at 37° C. After further rinsed 3 times with PBS, 100 μl phage culture supernatant as detailed above was added and incubated for 90 min at 37° C. The phage solution was discarded and the wells were washed 6 times with PBST and 6 times with PBS then an appropriate dilution of HRP-anti-M13 antibody in 5% MPBS was added. The mixture was incubated for 60 min at 37° C., and washed 6 times with PBST and 6 times with PBS. The wells were developed with substrate solution (TMB) and the reactions were stopped by adding 50 μl of 1 M sulfuric acid. The color turned yellow, and the OD at 650 nm and at 450 nm was assayed.

After screening, total 379 clones and 66 kinds of CDRH3 are identified.

Expression of Full-Length Antibodies

The genes encoding the V_(H) and V_(L) chains of anti-VEGFR2 antibodies were inserted into an expression vector. Free-style 293 cells were transfected with the vector constructed. Follow the procedure below to transfect suspension FreeStyle™ 293 cells in a 30 ml volume. Approximately 24 hrs before transfection, pass FreeStyle™ 293 cells at 2×10⁶ cells/ml for 15 ml. Place the flask(s) at 37° C., 8% CO₂ incubator. Then dilute 37.5 pg of plasmid DNA into 1.5 ml of sterile 150 mM NaCl to a total volume of 1.5 ml. In a separate tube, dilute 37.5 μL of PEI (2.0 mg/ml) in 1.5 ml of sterile 150 mM NaCl. Stand DNA and PEI solution at room temp for 5 minutes, mix gently by inverting the tube and stand at room temp around 10-20 minutes. Immediately add DNA-PEI mixture into F293 cells and incubate transfected cells on an orbital shaker platform rotating at 135-150 rpm at 37° C., 8% CO2 incubator for 4 hours. Then add equal volume fresh culture medium to a total volume of 30 ml and culture during 5-7 days. Cells were harvested for protein purification and quantification.

Total 78 colonies are identified, including 322A6 and 12A6.

Binding Affinity Assay

An ELSA plate was coated with 100 μL per well of human VEGFR-2, mouse VEGFR2, human VEGFR1 or human VEGFR3 overnight at 4° C., and then rinsed 3 times with PBS and blocked with 300 μL per well of 5% MPBS for 2 hr at 37° C. The wells were rinsed 3 times with PBS, and 100 μL of anti-VEGFR2 antibody, 2 fold serial dilutions, was added and incubated for 90 min at 37° C. The test solution was discarded and washed 3 times with PBS. Appropriate dilution of HRP-anti-Human IgG antibody in 5% MPBS (1:10000) was added and incubated for 60 min at 37° C., and the wells were washed 3 times with PBS. The wells were developed with 100 μL of substrate solution TMB and the reactions were terminated by adding 50 μL of 1 M sulfuric acid. The color turned yellow and the OD at 650 nm and at 450 nm was assayed.

The results of binding affinity of several antibodies are shown in FIG. 1 and Table 1. It shows that 12A6 and 322 A6 antibodies have binding affinity to human VEGFR-2. 322A6 antibody has binding affinity to mouse VEGFR-2, but has no affinity to human VEGFR-1 and VEGFR-3. Thus, 322A6 is specific to VEGFR-2.

TABLE 1 Analyte VEGFR-2 (domains 1 to 7) Rmax Chi² Antibodies K_(a) K_(d) K_(D) (RU) (RU²) 12A6 4.488E+4 2.066E−4 4.604E−9  276.9 0.457 322A6 8.247E+5 5.547E−4 6.726E−10 102.2 4.29

The sequences of CDRs of 322A6 and 12A6 are shown in Table 2. 322A6 comprises a heavy chain variable region comprising the amino acid sequences of SEQ ID NO: 17, and the heavy chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 16. 322A6 comprises a light chain variable region comprises the amino acid sequence of SEQ ID NO: 19, and the light chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 18. 12A6 comprises a heavy chain variable region comprising the amino acid sequences of SEQ ID NO: 21, and the heavy chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 20. 12A6 comprises a light chain variable region comprises the amino acid sequence of SEQ ID NO: 23, and the light chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 22.

TABLE 2 Sample CDRH1 CDRH2 CDRH3 CDRL1 CDRL2 CDRL3 322A6 GYAFTTY MIDFSDS DVRGNF RASKSVS LASNLES QHSRELP WMH ETKLNQR DV (SEQ TSGYSYM (SEQ ID WT (SEQ (SEQ ID FKG (SEQ ID NO: 6) H (SEQ ID NO: 8) ID NO: 9) NO: 4) ID NO: 5) NO: 7) 12A6 GYSFTDY YIDPYND GYADAM HASQNIN KASNLHT QQGQSYP SMY (SEQ DTSYKQK DY (SEQ VWLS (SEQ ID LT (SEQ ID NO: 10) FKG (SEQ ID NO: 12) (SEQ ID NO: 14) ID NO: 15) ID NO: 11) NO: 13)

Domain Mapping Assay

Fragments of human VEGFR-2 were constructed. The fragments were utilized to binding affinity assay as mentioned above. The result of domain mapping is shown in FIGS. 2 and 3 and Tables 3 and 4.

TABLE 3 Binding domain 322A6 (45) 12A6 R2 D1-2 − − R2 D1-3 − − R2 D1-4 − − R2 D1-5 − − R2 D1-6 − +++++ R2 D1-7 +++++ +++++ R2 D6-7 +++++ +++++ R2 D6 − +++ R2 D7 ++++ ++++

TABLE 4 Sample Binding Domain 322A6 7 12A6 6-7

Epitope Mapping

In domains 6 (SEQ ID NO: 2) and 7 (SEQ ID NO: 3) of human VEGFR-2, several point mutants were constructed. The mutants were utilized to binding affinity assay as mentioned above. The positions of the mutation sites are shown in FIG. 4. The epitope of 12A6 comprises the leucine residue at position 606, the aspartic acid residue at position 607, the arginine residue at position 647, the lysine residue at position 648, and the threonine residue at position 649. The epitope of 322A6 comprises the serine residue at position 711, the valine residue at position 714, and the arginine residues at positions 725 and 726.

Anti-VEGF R2 Ab-HUVEC Proliferation Inhibition Assay

Materials: HUVEC (Cascade Biologics, Cat No. C-003-5C), Medium 200 (Cascade Biologics, Cat No. M-200-500), Hybridoma medium (10% FBS-DMEM), FBS (Hyclone, #SH30071.03), DMEM (GIBCO, #11995), Human CHO VEGF, hVEGF (PROSPEC, Cat No. CYT-260), anti-VEGFR2, WST-1 (Roche, Cat No. 11644807001).

One-hundred μL of antibody sample in 10% FBS-DMEM was inoculated to each well of a 96 well plate, and every sample was duplicated. The cells were harvested and suspended in Medium 200 at 8×10⁴ cells/ml, and incubated for 30 mins at 37° C., 5% CO₂. The hVEGF was diluted in Medium 200 at 50 ng/ml, and 50 μL of standard hVEGF was added to the plate for incubating for 96 hours at 37° C., 5% CO₂. Then, 20 μL of WST-1 was added to each well and incubated for 4 hours at 37° C., 5% CO₂. The absorbance (OD450-655 nm) was measured using the ELISA reader.

The result of proliferation assay is shown in FIG. 5. As shown in FIG. 5, when the concentrations of the antibody are higher, the effect of VEGFR-2 signal inhibition is stronger, and the number of HUVEC (OD450-655 nm) is less. Among the antibodies, 12A6 has the strongest effect with IC50=3.9 μg/ml.

Internalization of Anti-VEGFR-2 Antibodies into HUVEC

The internalization of antibody into HUVECs was analyzed with the flow cytometry.

Flow cytometry (CytoFLEX) Cell line: HUVEC

1st Antibodies: 322A6

2nd Antibody: Goat anti-Human Kappa Light Chain, Bethyl, Cat.A80-115F Medium 200 (M200), Thermo, Cat. C-003-25P-A, Low Serum Growth Supplement (LSGS). Cat. S00310 FBS (Gibco, Cat. 10082-147), FACS buffer (1×PBS, 1% FBS, 0.02% NaN3) 15-mL Falcon tube (Corning, Cat. CS352096)

T150: Tissue Culture Flasks (TPP, 90150)

The cell number of HUVEC was counted, and mixed with 322A6 and incubated on ice for 1 hr. The cells were collected by spinning and washed by 10 mL of ice-cold FACS buffer three times. 2×10⁵ cells/rxn/well (24-well plate) were seeded in RPMI medium w/2% FBS, and then incubated at 37° C. or 4° C. for indicated period. At each time point, the cells were washed by 10 mL of ice-cold FACS buffer, and 2nd antibody (α-hIgG-FITC, 1:200 diluted by ice-cold FACS buffer) was added on ice for 1 hr. After washed by 10 mL of ice-cold FACS buffer three times, the cells were seeded (2*10⁵ cells/rxn/tube by FACS buffer) and incubated at 37° C. or 4′C for indicated period. At each time point, the cells were suspended and analyzed by Flow cytometry & CytExpert software.

The result is shown in Table 5 and FIG. 6. Before antibody internalization happening (0 min), the HUVEC cell bound with the antibody is detected with flow cytometry. After antibody internalization happening, the antibody is translocated from the surface of the cell to the endosome inside the cell, and the signal of flow cytometry disappears. Thus, if an antibody has strong tendency of antibody internalization, the relative binding with the target cell is lower. As can be seen in Table 5 and FIG. 6, 322A6 has the stronger tendency of antibody internalization.

TABLE 5 Cell population (%) Time (min) 322A6 3 32 59 80 0 31.4 18.1 38.7 31.1 39.9 10 25.1 18.6 35.3 27.0 34.0 30 21.6 17.5 33.7 20.6 35.9 60 15.1 15.1 29.3 17.0 32.9 90 6.8 1.1 25.7 14.6 7.5 120 1.7 3.7 16.1 5.9 5.2

The antibody internalization was also observed under the microscope with the DeltaVision Microscopy Imaging System, and shown in FIG. 7. Rab5a was taken as a positive control, and DAPI was used for labeling nuclei. By labeling 322A6 and endosome simultaneously, it shows that 322A6 is successfully internalized into the cell.

Conjugation of Anti-VEGFR2 Antibody with Romidepsin

322A6 (C45) antibody was conjugated with Romidepsin, also known as Istodax, an anticancer agent, according to the following scheme:

The condition of conjugation is listed in Table 6.

TABLE 6 TMB355-SMCC- ADC (antibody- Lot No. 322A6 Romid-Spy drug conjugate) 14- 1 mg SMCC-Romid-SPy(160413- Conc: 4.06 μg/μl 0151- 1) in DMA: (Recovery rate: 73%) 00-01 10 mM, 24 eq Aggregate: 2.1% Conc.: 5 mg/ml DAR: 1.93 37° C., 17 h

The obtained antibody-drug conjugate (ADC) (11-0151-00-01) was analyzed with size-exclusion chromatography (SEC):

Column: Superdex 200 Increase 10/300 GL (GE)

Sample: IgG & IgG-ADC, 0.3 mg/mL Sample volume: 100 μL Flow rate: 0.5 mL/min

Buffer: lx PBS System: ÅKTA

The result of chromatography is shown in FIG. 8 and Table 7. The ADC was also subjected to electrophoresis and shown in FIG. 9.

TABLE 7 c45 14-0151-00-01 (322A6) (ADC of 322A6) Retention Peak Area Retention Peak Area (mL) (%) (mL) (%) Aggregates — 0.0 7.74 2.1 IgG dimer 10.61 3.3 10.42 6.0 IgG Monomer 12.46 95.4 12.34 91.3 Fragments 19.22 + 20.30 1.3 19.15 0.6

As shown in FIG. 8, the obtained antibody-drug conjugate has 95.4% of monomer and 95% of purity.

The internalization of the ADC was also assayed as mentioned above. The result is shown in FIG. 10, and the tendency of internalization in the ADC of 322A6 is similar to that in 322 A6 antibody only (c45).

The inhibition of HUVEC proliferation of the ADC was also assayed as mentioned above. The result is shown in FIG. 11. The effect of 322A6 antibody only (c45) in inhibiting HUVEC proliferation was mild. It means that the blocking effect of 322A6 antibody in VEGFR-2 signal transduction is not very strong. However, when treated 322A6 conjugated with Romidepsin (c45-ADC), the relative cell viability of HUVEC is dropped significantly. Not to be limited by theory, it is believed that the drop of relative cell viability of HUVEC is resulted from the cytotoxicity of the ADC of 322A6 antibody instead of from the inhibition of HUVEC proliferation.

Chimeric Antigen Receptor T-Cell (CAR-7) Immunotherapy

Peripheral blood mononuclear cells (PBMCs) were isolated from healthy donors and stimulated with Dynabeads® Human T-Activator CD3/CD28 (Gibco) in RPMI with 10% FBS (hyclone) and 100 U/mL recombinant interleukin-2 (Roche) for 48 hr. Activated T cells were collected using the Pan T-Cell Isolation Kit, human (Miltenyi Biotec) according to the manufacturer's protocol. Lentiviral vector contained the single-chain variable fragment of anti-VEGFR-2 antibody, and the signaling domains of 4-1BB and CD3-z. Viral supernatants were produced by transient transfection of HEK293T cells with the transfer genome plasmid and lentiviral packaging helper plasmids pMD2.G and pCMVΔR8.91 and used to transduce human T cells on RetroNectin-coated plates (TaKaRa Bio Inc.). Transduction efficiency was analyzed by flow cytometry.

The result is shown in FIG. 12. The quantification analysis shows that 5.1%, 10.4% and 7.79% of 1121, 12A6 and 322A6 CAR expressed on the T cells, respectively.

Cytotoxicity Assay of Antigen Receptor T-Cell

Cytotoxic activity was measured by using the Cytotoxicity Detection Kit (Roche, Indianapolis, Ind., USA) according to the manufacturer's instructions. Anti-VEGFR-2 CAR T cells were incubated with the VEGFR2 positive cell lines at the indicated E:T ratios for 16 hr at 37° C. Percent-specific cytolysis was calculated by using the formula: (Test-effector control-low control/high control-low control)*100. High control is calculated after incubating target cells in 1% Triton X 100; effector control is the spontaneous LDH release value of T cells alone; low control is the spontaneous LDH release value of target cells alone. Effector cells: primary T cell transduced with anti-VEGFR-2 CAR (5 days post 1st transduction). Target cells: FS293 (overexpressed VEGFR-2). Effector cells and target cells were co-cultured for 16 hours.

A scFv fragment of CD19 was also used for manufacturing a CAR-T as a control (CD19). T cell only was also taken as a control (T). 1121 antibody was a known anti-VEGFR-2 antibody that specifically binds to domains 2 and 3 of the VEGFR-2, which domains are far away from the cell membrane in the VEGFR-2. CAR-T of 1121 was used in the assay for comparison. The result is shown in FIG. 13. The CAR-Ts of 12A6 and 322A6 both have stronger cytotoxicity than the CAR-T of 1121. Not to be limited by theory, it is believed that 12A6 and 322A6 antibodies specifically bind to domains 6 and/or 7 of the VEGFR-2, which are near the cell membrane in the VEGFR-2.

Producing Radioactive-, Iodine-Bound Antibody

One ml of 25 mM Tris-HCl (pH7.5) and 0.4 M NaCl buffer solution was added to an IODO-gen tube, and then discarded. One hundred μl of buffer solution was added to the tube, and then 1 μl of I-123 or I-131 was added for reacting at room temperature for 6 minutes with gently shaking. The anti-VEGFR-2 antibodies were added for reacting at room temperature for 6 to 9 minutes with gently shaking. The reaction was terminated by transferring the reactants into a new eppendorf tube. The efficiency of the labeling process was analyzed by Radio-TLC with the developing solution of 85% methanol and ITLC/SG paper.

The efficiency of the labeling process ¹³¹I-anti-VEGFR-2-clone 45(322A6) is shown in FIG. 14. More than 96.8% of antibodies were labeled.

Stability of Radioactive Iodine-Bound Antibody in Serum

The labeled antibodies and serum derived from human or rat were mixed with the volume ratio of 1:19 and reacted at 37° C. At hour 0.25, 0.5, 1, 4, 8, 24, 48, and 72, 800 μl of 10% TCA was added to 10 μl of the sample and mixed. Proteins contained in the sample were precipitated by ice bath for 15 minutes. The supernatant was filtered with 0.45 μm PVDF membrane and the ratio-activity of the liquid was counted presenting the dissociated 1-131. Stability=(activity before filtration−activity after filtration)/activity before filtration.

The result is shown in Table 8 revealing that ¹³¹I-anti-VEGFR-2-clone-45 does not degraded in serum in 72 hours.

TABLE 8 Radio-bound stability of ¹³¹I-antiVEGFR-2- c45 in human and rat serum, % Time (hr) Human serum Rat serum 0 95.06 ± 0.59 89.95 ± 7.08 0.25 94.51 ± 0.68 91.67 ± 5.89 0.5 94.54 ± 0.58 93.11 ± 4.58 1 93.59 ± 0.68 92.52 ± 5.16 4 94.54 ± 0.66 93.56 ± 4.41 8 94.61 ± 0.67 93.65 ± 4.29 24 94.47 ± 0.49 93.21 ± 4.64 48 94.33 ± 0.64 93.06 ± 4.75 72 94.38 ± 0.61 93.17 ± 4.59 Detecting Tumor with Radioactive Iodine-Bound Antibody

SPECT/CT was utilized for detecting tumor with the radio-bound antibody according to the invention. The HT-29 xenografted mice were i.v. injected with 4 to 8 μCi/μg of radio activity. Each mouse was administrated with 1 to 2 mg/kg B.W. ¹³¹I or ¹²³I labeled anti-VEGFR2 antibody. At hour 1, 4, 24, and 48, the mice were scanned with SPECT/CT.

The result is shown in FIG. 15. The result reveals that the radio-bound antibody 322A6 is able to specifically bind to the HT-29 xenografted tumor and the radioactive signal is accumulated in the tumor. The strongest signal appears at hour 18 in the tumor. The antibodies are degraded after hour 18, and almost all antibodies are degraded after hour 48.

Combination Therapy

Male B6 (C57BL/6JNarl) mice, aged 6 to 8 weeks old, were taken as the animal model. The mice were fed under a 12-hr light/dark cycle and received ad lib access to PMI feeds (RMH3000-5P76) and water. The mice were grouped as:

Group 1: IgG (Mu) (nonfunctional IgG antibody), 15 mpk/i.v., twice/week, n=6 Group 2: αCTLA-4 (Mu), 5 mpk/i.v.+IgG (Mu), 10 mpk/i.v., twice/week, n=6 Group 3: αCTLA-4 (Mu), 5 mpk/i.v.+322 A6, 10 mpk/i.v., twice/week, n=6 Group 4: IgG (Mu), 5 mpk/i.v.+322 A6, 10 mpk/i.v., twice/week, n=6

The tumor sizes were measured and listed in Table 9. The combination of anti-CTLA4 antibody and anti-VEGFR-2 antibody (322A6) has synergistic effect.

TABLE 9 Tumor volume (mm³) Day 0 Day 4 Day 7 Day 11 Day 14 Day 21 IgG (Mu), 15 mpk 0.0 0.0 30.9 195.3 866.2 3540.5 αCTLA-4 (Mu) 5 mpk + IgG (Mu) 10 mpk 0.0 0.0 5.4 211.0 634.6 2425.5 αCTLA-4 (Mu) 5 mpk + 322A6 10 mpk 0.0 0.0 12.7 86.9 365.0 1140.3 IgG (Mu) 5 mpk + 322 A6 10 mpk 0.0 0.0 3.0 174.7 739.5 3240.9

The body weights were also measured and listed in Table 10, and it reveals that the body weights of all the groups are substantially the same.

TABLE 10 Body Weight (gm) 0 day 4 day 7 day 11 day 14 day 21 day IgG (Mu), 15 mpk 25.1 26.2 26.2 26.1 26.1 31.7 αCTLA-4 (Mu) 5 mpk + IgG (Mu) 10 mpk 25.0 25.0 25.8 25.6 25.5 28.7 αCTLA-4 (Mu) 5 mpk + 322A6 10 mpk 25.6 25.6 26.2 26.2 26.1 28.2 IgG (Mu) 5 mpk + 322A6 10 mpk 25.4 25.4 26.4 26.2 26.8 31.8

Humanization of Antibody

Selection of human V region framework: Sequences selection of human V region framework sequences human germ-line V_(L) and V_(H) sequences with the highest degree of homology with the 322A6 framework regions were identified from IMGT database (http://www.imgt.org/) and commonly used VH3/Vk1(4D5). Finally, framework sequences of VH3 and Vk1 were selected for the VH framework and the VL framework, respectively. Humanized framework marked as Hu was come from IMGT database and Hd series were from 4D5 framework.

Full length CDR grafted Ab Construction: 322A6 (HH) consisted complete human framework (VL κ subgroup I and V_(H) subgroup III) with the six complete murine CDR sequences. The 322A6(HH) and half humanized (MH or HM) antibody construct were assembled by PCR and restriction enzyme digestion for directional sub-cloning into modified antibody expression vector pTCAE8.3. The plasmid contains a DNA fragment encoding human kappa light-chain and human IgG1 C region. The full length antibody was expressed in Free-style 293 cells.

Back mutation: Clone 322A6(HuB1-Hd) was selected for 1-3 run back mutation from CDR grafted framework for binding activity recovery. Briefly, we perform analysis CDR grafting framework by computer modeling that to examine by a 5 Å proximity, upper core region, interface area and also apply previous experience of most commonly used in successful cases. We had selected 3 run, that 5˜11 possible amino acid back mutation. These sites were recognized as important sites for CDR binding and structure. After cloning and antibody expression, binding activity was determined by ELISA and BIAcore. The combination clone of heavy chain (HuB1) and light chain (Hd) with 7 amino acid back mutation (7+0) was the suitable candidate for VEGFR2 binding.

A humanized antibody Hu322B1HdH was constructed with a heavy chain variable region comprising the amino acid sequences of SEQ ID NO: 25 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 27. The heavy chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 24 and the light chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 26. The alignment of V_(L) segments is shown in FIG. 16, and the alignment of V_(H) segments is shown in FIG. 17.

While the present invention has been described in conjunction with the specific embodiments set forth above, many alternatives thereto and modifications and variations thereof will be apparent to those of ordinary skill in the art. All such alternatives, modifications and variations are regarded as falling within the scope of the present invention. 

What is claimed is:
 1. An antibody or antigen-binding fragment thereof that specifically binds to an epitope in human vascular endothelial growth factor receptor 2 (VEGFR-2) or a fragment thereof; wherein the human vascular endothelial growth factor receptor 2 has the amino acid sequence of SEQ ID NO: 1, and the epitope comprises: the leucine residue at position 606, the aspartic acid residue at position 607, the arginine residue at position 647, the lysine residue at position 648, and the threonine residue at position 649 of SEQ ID NO: 1; or the serine residue at position 711, the valine residue at position 714, and the arginine residues at positions 725 and 726 of SEQ ID NO:
 1. 2. The antibody or antigen-binding fragment thereof according to claim 1, which is a mammalian antibody.
 3. The antibody or antigen-binding fragment thereof according to claim 1, which comprises complementarity determining regions (CDRs) of a heavy chain variable region and complementarity determining regions of a light chain variable region, wherein the complementarity determining regions of the heavy chain variable region comprises CDRH1, CDRH2 and CDRH3 regions, and the complementarity determining regions of the light chain variable region comprises CDRL1, CDRL2 and CDRL3 regions, and the CDRH1 region comprises the amino acid sequence of SEQ ID NO: 4 or a substantially similar sequence thereof; the CDRH2 region comprises the amino acid sequence of SEQ ID NO: 5 or a substantially similar sequence thereof; the CDRH3 region comprises the amino acid sequence of SEQ ID NO: 6 or a substantially similar sequence thereof; the CDRL1 region comprises the amino acid sequence of SEQ ID NO: 7 or a substantially similar sequence thereof; the CDRL2 region comprises the amino acid sequence of SEQ ID NO: 8 or a substantially similar sequence thereof; and the CDRL3 region comprises the amino acid sequence of SEQ ID NO: 9 or a substantially similar sequence thereof.
 4. The antibody or antigen-binding fragment thereof according to claim 1, which comprises complementarity determining regions of a heavy chain variable region and complementarity determining regions of a light chain variable region, wherein the complementarity determining regions of the heavy chain variable region comprises CDRH1, CDRH2 and CDRH3 regions, and the complementarity determining regions of the light chain variable region comprises CDRL1, CDRL2 and CDRL3 regions, and the CDRH1 region comprises the amino acid sequence of SEQ ID NO: 10 or a substantially similar sequence thereof; the CDRH2 region comprises the amino acid sequence of SEQ ID NO: 11 or a substantially similar sequence thereof; the CDRH3 region comprises the amino acid sequence of SEQ ID NO: 12 or a substantially similar sequence thereof; the CDRL1 region comprises the amino acid sequence of SEQ ID NO: 13 or a substantially similar sequence thereof; the CDRL2 region comprises the amino acid sequence of SEQ ID NO: 14 or a substantially similar sequence thereof; and the CDRL3 region comprises the amino acid sequence of SEQ ID NO: 15 or a substantially similar sequence thereof.
 5. The antibody or antigen-binding fragment thereof according to claim 1, which comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 17 or a substantially similar sequence thereof, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 19 or a substantially similar sequence thereof.
 6. The antibody or antigen-binding fragment thereof according to claim 5, wherein the heavy chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 16; and the light chain variable region is encoded by a nucleic acid sequence of SEQ ID NO:
 18. 7. The antibody or antigen-binding fragment thereof according to claim 1, which comprises a heavy chain variable region comprising the amino acid sequences of SEQ ID NO: 21 or a substantially similar sequence thereof; and a light chain variable region comprising the amino acid sequences of SEQ ID NO: 23 or a substantially similar sequence thereof.
 8. The antibody or antigen-binding fragment thereof according to claim 7, wherein the heavy chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 20; and the light chain variable region is encoded by a nucleic acid sequence of SEQ ID NO:
 22. 9. The antibody or antigen-binding fragment thereof according to claim 1, which comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 25 or a substantially similar sequence thereof; and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 27 or a substantially similar sequence thereof.
 10. The antibody or antigen-binding fragment thereof according to claim 9, wherein the heavy chain variable region is encoded by a nucleic acid sequence of SEQ ID NO: 24 the light chain variable region is encoded by a nucleic acid sequence of SEQ ID NO:
 26. 11. The antibody or antigen-binding fragment thereof according to claim 1, which is conjugated with a therapeutic agent.
 12. The antibody or antigen-binding fragment thereof according to claim 11, wherein the therapeutic agent is selected from the group consisting of antimetabolites, alkylating agents, alkylating-like agents, DNA minor groove alkylating agents, anthracyclines, antibiotics, calicheamicins, antimitotic agents, topoisomerase inhibitors, HDAC inhibitor, proteasome inhibitors, and radioisotopes.
 13. The antibody or antigen-binding fragment thereof according to claim 1, which is expressed on a surface of a cell.
 14. The antibody or antigen-binding fragment thereof according to claim 13, wherein the cell is a T-cell.
 15. A method for inhibiting VEGFR-2-mediated signaling in a subject in need, comprising administering to the subject a pharmaceutical composition comprising the antibody or antigen-binding fragment thereof according to claim
 1. 16. A method for treating diseases and/or disorders caused by or related to VEGFR-2 activity and/or signaling in a subject afflicted with the diseases and/or disorders, comprising administering to the subject a pharmaceutical composition comprising the antibody or antigen-binding fragment thereof according to claim
 1. 17. A method for treating tumor in a subject afflicted with the tumor, comprising administering to the subject a pharmaceutical composition comprising the antibody or antigen-binding fragment thereof according to claim
 1. 18. The method according to claim 17, wherein the tumor is a solid tumor.
 19. The method according to claim 18, wherein the tumor is selected from the group consisting of renal cell carcinoma, pancreatic carcinoma, breast cancer, head and neck cancer, prostate cancer, malignant gliomas, osteosarcoma, colorectal cancer, gastric cancer, malignant mesothelioma, multiple myeloma, ovarian cancer, small cell lung cancer, non-small cell lung cancer, synovial sarcoma, thyroid cancer, or melanoma.
 20. A method for inhibiting cell proliferation of endothelial cells in a subject in need, comprising administering to the subject a pharmaceutical composition comprising the antibody or antigen-binding fragment thereof according to claim
 1. 21. A method for detecting human vascular endothelial growth factor receptor 2 in a sample comprising contacting the sample with the antibody or antigen-binding fragment thereof according to claim
 1. 22. The method according to claim 21, which is for detecting domains 6 to 7 of the VEGFR-2. 